在 2008-07-08二的 22:02 +0200，Jan Kara写道： > > Eric Sandeen wrote: > > >Mingming Cao wrote: > > > > > >>ext4: delayed allocation i_blocks fix for stat(2) > > >> > > >>From: Mingming Cao <cmm@xxxxxxxxxx> > > >> > > >>Right now i_blocks is not getting updated until the disks are actually > > >>allocaed on disk. This means with delayed allocation, right after files > > >>are copied, "ls -sF" shoes the file as taking 0 blocks on disk. "du" > > >>also shows the files taking zero space, which is highly confusing to the > > >>user. > > >> > > >>Since current delayed allocation already keep track of per-inode total > > >>number > > >>of blocks that are subject to delayed allocation, this patch fix this by > > >>using > > >>that to adjust the value returned by stat(2). When real block allocation > > >>is done, the i_blocks will get updated. Since the reserved blocks for > > >>delayed > > >>allocation will be decreased, this will be keep value returned by stat(2) > > >>consistent. > > >> > > >>Signed-off-by: Mingming Cao <cmm@xxxxxxxxxx> > > >> > > > > > >Thanks Mingming, looks like just the right approach. > > > > > >Something about the spinlock for every stat seems heavy-handed to me but > > >I'll have to give that more thought. :) > > > > > > > > > > Since i_reserved_blocks is an unsigned long, it should be possible > > to atomically fetch it on all of the supported architectures, > > without the use of the spinlock. It seems to me that this spinlock > > is not required here. > Well, it's certainly not nice to rely on this. The clean solution > would be to convert i_reserved_blocks to atomic_t or atomic64_t on archs > that have it... > I was thinking about the same thing when this lock was initially introduced ... but this lock is protecting three counters, and these counters are updated/reset in a couple of places, and being used to calcuate how much per-fs free blocks counter need to be accounted. It's doable, just need a careful look if we make them all atomic. Mingming > Honza -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
